Piezoelectric buzzer assembly

ABSTRACT

A piezoelectric buzzer in which a vibrator comprising a piezoelectric element and a vibrating disc integrally connected together is vibratorily mounted within a casing at least the front wall of which is provided with openings and the vibrator is electrically connected to an electric oscillation circuit provided within or outside of the casing whereby vibration of the vibrator due to strain generates acoustic waves.

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21 Appl. No.: 372,079

Primary Examiner-Mark O. Budd Attorne A t, F'rm-Kurt Kelm' n [30] Foreign Application Priority Data y gen or I d June 26, 1972 ABSTRACT A piezoelectric buzzer in which a vibrator comprising a piezoelectric element and a vibrating disc integrally connected together is vibratorily mounted within a casing at least the front wall of which is provided with 0 M w 17 Hub w 1H 1 W 9 2 n I 0 B a m 1 H3 mh c ur. "a e S 1 m m min IF ,1] 118 55 .11

310/9.4;179/110 A; 181/31 R, 31 A, 31 B,

References Cited UNITED STATES PATENTS 2,702,318 Dvorsky...................... 179/110 A X 6 Claims, 5 Drawing Figures PRIOR ART' Fig. 2

PRIOR ART I PATENTEDJAN 1 4197s saw an! 2 PIEZOELECTRIC BUZZER ASSEMBLY BACKGROUND OF THE INVENTION This invention relates to piezoelectric buzzers and more particularly, to an improved piezoelectric buzzer which comprises a vibrator including a piezoelectric element and a vibrating disc integrally connected together and an electric oscillation circuit electrically connected to the vibrator and which is used as a fire alarm, burglar alarm, gas detector alarm, interphone or clockwork buzzer.

Generally, a piezoelectric buzzer comprises a vibrator including a piezoelectric element and a vibrating disc integrally connected together, a casing receiving the vibrator for vibratory movement therein and an electronic oscillation circuit connected to the piezoelectric element and vibrating disc to apply electric signals to the vibrator so as to cause the vibrator to vibrate due to strain and the vibration of the vibrator generates acoustic waves.

The front wall of the casing which receives the vibrator has on the inner side thereof an integral resonant cylinder which extends axially of the casing from the front wall towards the vibrator and the resonant cylinder is designed to resonate acoustic waves generated from the vibration of the vibrator so as to amplify the acoustic volume of such acoustic waves. Such a casing has been customarily provided with openings so that resonated acoustic waves can be effectively emitted out of the casing. However, the conventional piezoelectric buzzer has been formed with such openings in only the front wall and in consequence, the amplification of generated acoustic volume in the conventional buzzer has been limited to a relatively narrow range. For example, in the conventional piezoelectric buzzers, the acoustic volume has been on the order of 87 dB at the utmost l in. short of them. Then I had proposed the buzzer with openings in both the front and side walls. With this structure, the acoustic volume was increased to 96 dB. But it has been quite difficult to amplify the acoustic volume in excess of lOO dB.

SUMMARY OF THE INVENTION Therefore, one principal object of the present invention is to provide a piezoelectric buzzer which can effectively amplify acoustic waves generated by the vibration of the vibrator without any increase in the size of the vibrator and/or power consumption.

Another object of the present invention is to substantially amplify acoustic volume generated in a piezoelectric buzzer by the use of a casing having an improved construction for receiving the vibrator of a piezoelectric acoustic means.

For attaining the above objects, according to the present invention, the piezoelectric buzzer casing in which the vibrator is received is encircled by a horn member.

According to the present invention, there has been provided a piezoelectric buzzer assembly which comprises acoustic means, said acoustic means comprising a vibrator including a piezoelectric element and a vibrating disc integrally connected together, a casing for receiving said vibrator therein having openings in at least the front wall thereof and an electric oscillation circuit electrically connected to said vibrator; and a horn member flaring forwardly thereof, the diameter of which reduces from one end remote from said acoustic means towards the other end adjacent to the acoustic means.

The above and other objects and attendant advantages of the present invention will be more apparent to those skilled in the art from a reading of the following detailed description in conjunction with the accompanying drawings which show preferred embodiments of the invention for illustration purpose only, but not for limiting the same in any way.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view showing the principle of a piezoelectric buzzer;

FIG. 2 is a cross-sectional view of a conventional piezoelectric buzzer;

FIG. 3 is a cross-sectional view of one embodiment of piezoelectric buzzer assembly of the present invention;

FIG. 4 is another cross-sectional view of a fourth embodiment of piezoelectric buzzer assembly of the present invention; and

FIG. 5 is a cross-sectional view of yet another embodiment of piezoelectric buzzer assembly of the present invention.

PREFERRED EMBODIMENTS OF THE INVENTION The present invention will be now described referring to the accompanying drawings which show various embodiments of piezoelectric buzzer assembly of the invention and a piezoelectric buzzer which I had proposed before for comparison purpose.

FIG. 1 shows the principle of a piezoelectric buzzer. A vibrator 2 which comprises a piezoelectric element 3 and a vibrating disc 4 integrally connected together is mounted on a suitable support member and the piezoelectric element and vibrating disc are electrically connected to an electric oscillation circuit 5, 6a, 6b. When current is allowed to flow through the vibrator 2, the vibrator is caused to strain at its support point on the support member and vibrate so as to generate acoustic waves.

FIG. 2 shows a piezoelectric buzzer which] had proposed before in cross-section. In the piezoelectric buzzer, a vibrator 2 is received in a cylindrical casing 7 and supported on projections 7g integrally formed with a partition wall 7c extending across the interior of the casing 7 to divide the interior into two chambers. The piezoelectric elements 3 and vibrating disc 4 of the vibrator 2 are electrically connected to an electric oscillation circuit means 5 through lead lines 6a and 6b,

respectively. The front wall of the casing 7 is provided with a plurality of openings 7e and the cylindrical side wall 7b of the casing is also provided in its periphcry with a plurality of openings 7f. Also integrally formed with and extending rearwardly of the front wall 7a of the casing 7 is a resonant cylinder 8 the free or inner end of which terminates short of the vibrator 2. Acoustic waves generated by the vibration of the vibrator 2 are resonated by the resonant cylinder 8 whereby the acoustic volume of the acoustic waves from the piezoelectric buzzer is amplified. The amplified acoustic waves are mainly emitted out of the buzzer through the openings in the front and side walls referred to above.

FIG. 3 shows one embodiment of a buzzer assembly of the invention in cross-section. Since the buzzer vibrator and electric oscillation circuit incorporated in this buzzer assembly of FIG. 3 are identical with the corresponding parts of FIG. 2 the vibrator and electric oscillation circuit are shown with the same reference numerals as those assigned to the corresponding parts of FIG. 2. The vibrator 2 is supported on a support member secured to a partition wall of the casing as will be described hereinbelow.

The casing 27 which receives the vibrator 2 and electric oscillation circuit 5 comprises a frusto-conical side wall 27b which merges at the outer edge with the peripheral edge of the front wall 270 and flares inwardly or rearwardly, a partition wall 27c which extends across the interior of the casing 27 in parallel to the front wall 27a to divide the interior of the easing into outer and inner chambers A and B and merges at the peripheral edge with the side wall 27b and a rear wall 27d which extends parallel to the front wall 27a. The front wall 27a is formed in its peripheral portion with a plurality of openings 27e and similarly, the side wall 27b is also provided in its periphery with a plurality of openings 27f. The interior of outer chamber A communicates with the atmosphere through openings 27e and 27f. Integrally formed with and inwardly or rearwardly extending from the front wall 27a is a resonant cylinder 28.

The rear wall 27d of the casing 27 is provided with an annular projection 27h which extends towards the partition wall 27c and fits in an annular recess 271' formed in the bottom of the side wall 27b. The side and rear walls 27b and 27d are connected together by means of adhesive, for example.

Secured to the partition wall 27c within the outer chamber A are support members 27g which support the vibrator 2, and the piezoelectric element 3 and vibrating disc 4 of the vibrator are electrically connected to the electric oscillation circuit 5 positioned within the inner chamber B through lead lines 6a and 6b, respectively. Since the details of the electric oscillation circuit 5 themselves do not constitute any part of the present invention, they will not be in detail described herein and it will be sufficient to explain that the electric oscillation circuit comprises as its essential parts a printed base plate 5a secured to the casing side wall 27b, a resistance 5b secured to the base plate 5a, transistor 50 and the like.

Disposed encircling the casing side wall 27b in peripherally spaced relationship to the latter is a hollow cylindrical horn member 29. The horn member 29 includes an outer longer cylindrical side wall 29b and an inner shorter frusto-conical side wall 29a which slopes inwardly towards the casing side wall 27b and merges at the outer or fore edge with the outer or fore edge of the horn member outer side wall 29b at an acute angle to the latter. The free inner edge of the inner side wall 29a terminates short of the casing side wall 27b and is positioned rearwardly of the openings 27f in the casing side wall 27b. The rear or inner edge 29d of the outer cylindrical wall 29b of the horn member frictionally engages forwardly extending annular projection 27j formed on the bottom wall 27d of the casing 27.

In the embodiment of FIG. 3, since the buzzer assembly includes the horn member 29 having the forwardly flaring inner side wall 29a, acoustic waves emitted out of the casing side wall 27b through the openings 27f therein are reflected towards the front side of the buzzer increasing the acoustic volume of the acoustic waves.

Furthermore, in the embodiment of FIG. 3, since the horn member 29 is radially spaced from the side wall 27b of the casing 27, a terminal 5d of the electric oscillation circuit 5 can be positioned in the annular space defined by the casing side wall and horn member. Therefore, the horn member also serves as a protective cover for the electric terminal 5d. In addition, since the rear edge 29d of the outer side wall 29b of the horn member 29 merely frictionally engages the projection 27j on the rear wall 27 of the casing 27, the horn member 29 can be easily detachably connected to the easmg.

FIG. 4 shows another embodiment of buzzer assembly of the invention. Buzzer assembly 30 of FIG. 4 is substantially similar to assembly 20 of FIG. 3 except for the components of the casing and horn member and, therefore, a detailed description of the similar components will be omitted in the explanation of the embodiment of FIG. 4.

The casing 37 of the piezoelectric buzzer in the embodiment of FIG. 4 comprises a front wall 37a, a stepped side wall including a smaller diameter cylindrical side wall portion 37b the diameter of which reduces towards the front wall 37a and a larger uniform diameter cylindrical side wall portion 37c which is connected to the smaller diameter cylindrical side wall portion 37b by a radial wall portion 37d which extends and connects between the rear edge of the cylindrical side wall portion 37b and the fore edge of the cylindrical side wall portion 370, a partition wall 37:: extending across the interior of the casing parallel to the front wall 37a in a position slightly above the junction between the smaller and larger diameter side wall portions to divide the interior of the easing into outer and inner chambers A and B and a rear wall 37f parallel to the front and partition walls 37a and 37e. As in the case of the embodiment of FIG. 3, the front wall 37a and smaller diameter side wall portion 37b are formed with openings 37g and 37h, respectively. The front wall 370 of the casing 37 is also provided with a resonant cylinder 38 which is formed integral with and extends rearwardly of the front wall 37a.

The outer surface portion of the smaller diameter side wall portion 37b adjacent to the radial wall portion 37d is provided with threads for the purpose to be described hereinbelow. A substantially cylindrical horn member 39 is provided surrounding the side wall portion 37b of the casing 37 and comprises a shorter and smaller diameter inner cylindrical wall 39a which has on the inner surface threads in engagement with the threaded outer surface portion of the casing smaller diameter side wall portion 37b, a longer and larger diameter cylindrical outer side wall 39b spaced radially of and in parallel to the inner side wall 390 and an intermediate sloped or frusto-conical wall 39c connecting the inner and outer side walls 39a and 39b and flaring forwardly.

In the embodiment of FIG. 4, the printed base plate 5a of the electric oscillation circuit 5 is supported by electric terminal support pins 5e which are securedtov and extend through the rear wall 37f of the casing 37.

The pin 5e not only support the printed base plate 5a,

but serve as a support for the terminal of the electric oscillation circuit and piezoelectric buzzer.

Also in the piezoelectric buzzer in the embodiment of FIG. 4, acoustic waves emitted out of the casing side wall portion 37b through the openings 37h therein are reflected forwardly towards the front side of the buzzer enhancing the acoustic effect of the acoustic waves.

Furthermore, in the buzzer assembly of FIG. 4, since the horn member 39 is threadedly connected to the casing 37 by means of the threads on the smaller diameter side wall portion 37a of the casing 37 and the threads on the shorter inner side wall 39a of the horn member, a mounting panel P can be inserted and firmly held in position between the horn member 39 and radial intermediate wall 37d of the casing 37 so that the buzzer assembly can be mounted on a wall or the like support structure. And since the buzzer assembly can be secured to a suitable support structure by means of the pins Be, the buzzer assembly of FIG. 4 can be secured to the support structure in various ways so that the buzzer assembly will have a wide variety of applications.

FIG. 5 shows still another embodiment of a buzzer assembly of the invention. The buzzer assembly 40 of FIG. 5 comprises a conventional buzzer 1a and a horn member 49 surrounding the buzzer. Thus, as to the buzzer la of FIG. 5, description will be made only of essential parts thereof.

As in the case of the embodiment of FIG. 6, the smaller diameter side wall portion 47a of the casing 47 is provided on the outer surface with threads and a horn member 49 similar to the horn member shown in FIG. 4 is threaded on the casing. Thus, also in the embodiment of FIG. 5, a mounting panel P can be inserted between the horn member 49 and casing 47 so that the buzzer assembly can be simply supported on a structure wall and the like and thus, also in the embodiment of FIG. 5, the acoustic volume can be effectively enhanced.

The acoustic volume of the piezoelectric buzzer l of FIG. 2 and those of the piezoelectric buzzer assemblies and as shown in FIGS. 3 and 4 were experimentally observed, respectively and the experimental results will be given in the following Table 1.

Table l Inventive piezoelectric buzzer assemblies Piezo- Piezoelec- Piezoelecelectric tric buzzer tric buzzer buzzer l assembly 20 assembly 30 Applied voltage 24 V p-p 24 V pp 24 V p-p Acoustic volume 1 in.

short of each piezoelectric 96 dB I05 dB I05 dB buzzer or buzzer assembly also experimentally observed and the experimental results will be given in the following Table 2.

Table 2 Piezoelectric Piezoelectric buzzer buzzer la assembly 40 Applied voltage 24 V p-p 24 p-p Acoustic volume I m. short of 9| dli 98 dB device Table 3 Piezoelectric buzzer having casing side wall provided with Piezoelectric buzzer having casing side wall provided with no opening opening Impedance of vibrator 480 ohms 310 ohms Acoustic volume I m. short of 87 dB 96 dB buzzer In each case, the vibrator comprised a piezoelectric element having a diameter of 35 mm. and a thickness of 0.5 mm., a phosphor bronze vibrating disc having a diameter of 50 mm. and a thickness of 0.5 mm. and a silver electrode, which were integrally connected together. Input voltage is 24 V.D.C., in both cases.

From the results given in the various tables referred to above, it will be appreciated that the acoustic volume of a piezoelectric buzzer can be effectively amplified by providing its casing side wall with openings and encircling the buzzer by a horn member.

In these embodiments, an inner side wall 29a of the horn member 29, and intermediate walls 39c and 490 of the horn members 39 and 49 are shown as taking the form of a frustum of a cone. However, they may take the form of a frustum of a pyramid or of a polygonal pyramid each flaring forwardly thereof.

While I have described what are presently considered preferred embodiments of a piezoelectric buzzer assembly of the present invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the inventive concept contained therein and encompassed by the appended claims to cover all changes and modifications that fall within the spirit and scope of my invention.

What is claimed is:

l. A piezoelectric buzzer assembly which comprises acoustic means comprising a vibrator including a piezoelectric element and a vibratile disc integrally connected therewith, a casing having an end wall and a cylindrical side wall, the vibrator being arranged in the casing, an electric oscillation circuit electrically connected to the vibrator, and a horn member disposed about the periphery of the casing and flaring radially outwardly thereof, the buzzer assembly comprising the improvement of combining l. a resonant cylinder integral with the end wall and extending into the casing,

a. the cylindrical side wall and the resonant cylinder defining an annular chamber in the casing surrounding the resonant cylinder, and

b. the end wall and cylindrical side wall defining openings communicating with the annular casing chamber, and

2. the horn member having a diameter reducing from a first end remote from the acoustic means to a second end adjacent thereto,

a. the horn member defining an acoustical chamber with the cylindrical side wall and the openings in the side wall communicating with the acoustical chamber.

2. The piezoelectric buzzer assembly of claim 1, wherein the casing has another end wall, projecting means is arranged along the periphery of the other end wall, and the horn member has an outer side wall portion radially spaced from the cylindrical side wall of the casing and a second wall portion flaring radially outwardly from the cylindrical casing side wall, the outer side wall portion having a first end frictionally engaging the projecting means for detachably mounting the horn member on the casing and a second end, and the second horn member wall portion having a first end merging with the second end of the outer side wall portion and a second end spaced from the cylindrical casing side wall, the outer side wall portion of the horn member and the cylindrical side wall of the casing defining an annular space therebetween.

3. The piezoelectric buzzer assembly of claim 2, further comprising an electrical terminal of the oscillation circuit arranged in the annular space between the outer side wall portion of the horn member and the cylindrical casing side wall.

4. The piezoelectric buzzer assembly of claim 1, further comprising a wall integral with, and radially extending from, the cylindrical casing side wall, and a threaded connection between the horn member and the cylindrical casing side wall adjacent the radially extending wall.

5. The piezoelectric buzzer assembly of claim 4, wherein the horn member has an inner cylindrical wall portion threadedly connected to the cylindrical casing side wall, an outer cylindrical wall portion radially spaced from the inner wall portion and having an end remote from the radially extending wall, and a wall portion flaring radially outwardly from the cylindrical casing side wall, the flaring wall portion connecting the remote end of the outer wall portion to the inner wall portion of the horn member.

6. A piezoelectric buzzer assembly which comprises acoustic means comprising a vibrator including a piezoelectric element and a vibratile disc integrally connected therewith, a casing having an end wall and a cylindrical side wall, the vibrator being arranged in the casing, an electric oscillation circuit electrically connected to the vibrator, and a horn member disposed about the periphery of the casing and flaring radially outwardly thereof, the buzzer assembly comprising the improvement of the horn member having an inner eylindrical wall portion, an outer cylindrical wall portion radially spaced from the inner wall portion, and a wall portion flaring radially outwardly from the cylindrical casing side wall, the flaring wall portion connecting one end of the outer wall portion to the inner wall portion, and a threaded connection between the inner wall portion of the horn member and the cylindrical casing side wall. 

1. a resonant cylinder integral with the end wall and extending into the casing, a. the cylindrical side wall and the resonant cylinder defining an annular chamber in the casing surrounding the resonant cylinder, and b. the end wall and cylindrical side wall defining openings communicating with the annular casing chamber, and
 1. A piezoelectric buzzer assembly which comprises acoustic means comprising a vibrator including a piezoelectric element and a vibratile disc integrally connected therewith, a casing having an end wall and a cylindrical side wall, the vibrator being arranged in the casing, an electric oscillation circuit electrically connected to the vibrator, and a horn member disposed about the periphery of the casing and flaring radially outwardly thereof, the buzzer assembly comprising the improvement of combining
 2. The piezoelectric buzzer assembly of claim 1, wherein the casing has another end wall, projecting means is arranged along the periphery of the other end wall, and the horn member has an outer side wall portion radially spaced from the cylindrical side wall of the casing and a second wall portion flaring radially outwardly from the cylindrical casing side wall, the outer side wall portion having a first end frictionally engaging the projecting means for detachably mounting the horn member on the casing and a second end, and the second horn member wall portion having a first end merging with the second end of the outer side wall portion and a second end spaced from the cylindrical casing side wall, the outer side wall portion of the horn member and the cylindrical side wall of the casing defining an annular space therebetween.
 2. the horn member having a diameter reducing from a first end remote from the acoustic means to a second end adjacent thereto, a. the horn member defining an acoustical chamber with the cylindrical side wall and the openings in the side wall communicating with the acoustical chamber.
 3. The piezoelectric buzzer assembly of claim 2, further comprising an electrical terminal of the oscillation circuit arranged in the annular space between the outer side wall portion of the horn member and the cylindrical casing side wall.
 4. The piezoelectric buzzer assembly of claim 1, further comprising a wall integral with, and radially extending from, the cylindrical casing side wall, and a threaded connection between the horn member and the cylindrical casing side wall adjacent the radially extending wall.
 5. The piezoelectric buzzer assembly of claim 4, wherein the horn member has an inner cylindrical wall portion threadedly connected to the cylindrical casing side wall, an outer cylindrical wall portion radially spaced from the inner wall portion and having an end remote from the radially extending wall, and a wall portion flaring radially outwardly from the cylindrical casing side wall, the flaring wall portion connecting the remote end of the outer wall portion to the inner wall portion of the horn member.
 6. A piezoelectric buzzer assembly which comprises acoustic means comprising a vibrator including a piezoelectric element and a vibratile disc integrally connected therewith, a casing having an end wall and a cylindrical side wall, the vibrator being arranged in the casing, an electric oscillation circuit electrically connected to the vibrator, and a horn member disposed about the periphery of the casing and flaring radially outwardly thereof, thE buzzer assembly comprising the improvement of the horn member having an inner cylindrical wall portion, an outer cylindrical wall portion radially spaced from the inner wall portion, and a wall portion flaring radially outwardly from the cylindrical casing side wall, the flaring wall portion connecting one end of the outer wall portion to the inner wall portion, and a threaded connection between the inner wall portion of the horn member and the cylindrical casing side wall. 